The problem is that I shouldn't have to do anything. The computer should be able to figure this stuff on its own - after all, that's the kind of task that they're good for.
Oh, the "computer" (read: the manufacturer) has it all figured out already, rest assured. They just don't want to give up on a few performance percentage points.
Or, more likely, selling you replacement batteries.
Ok, but at the same time, they could also tack some money on to the price for "batter life extending technology" and make money that way...